Planetary gear drive assembly

Abstract

A planetary gear drive assembly for a rotary sprinkler includes a drive housing in which a planetary gear train is enclosed. A turbine located beneath one end of the drive housing rotates the gear train through a turbine shaft that extends into the drive housing. An output shaft extends out of the other end of the drive housing for rotating the nozzle assembly of the rotary sprinkler. The drive assembly includes an alignment means for causing the planetary gears in each stage of the gear train to self align the planetary gears relative to an internal ring gear on the drive housing as each stage is slid into the drive housing during assembly. The alignment means comprises a stepped extension on a forward edge of the ring gear that extends around only a portion of the circumference of the ring gear.

We claim: 
     
       1. A planetary gear drive assembly, which comprises: (a) a drive housing having an internal ring gear on an inner diameter of the drive housing;   (b) a planetary gear train within the drive housing, wherein the planetary gear train includes at least one planetary gear stage comprising: (i) a central sun gear; and   (ii) a plurality of planetary gears spaced around and in engagement with an outer diameter of the sun gear such that rotation of the sun gear rotates the planetary gears, each planetary gear further being in engagement with the internal ring gear on the drive housing; and     (c) means for causing the planetary gears in each planetary gear stage to self align with the internal ring gear in an automatic fashion and without manual intervention responsive to the movement of each planetary gear stage towards the ring gear during assembly of each planetary gear stage within the drive housing.   
     
     
       2. The planetary gear drive assembly of claim 1, wherein the planetary gear train includes a plurality of planetary gear stages. 
     
     
       3. The planetary gear drive assembly of claim 1, wherein the self aligning means comprises a stepped extension extending in advance of a forward edge of the ring gear with the stepped extension further extending around only a portion of a circumference of the ring gear. 
     
     
       4. The planetary gear drive assembly of claim 3, wherein the stepped extension comprises first and second stepped portions. 
     
     
       5. The planetary gear drive assembly of claim 4, wherein each stepped portion has a height measured by how far forwardly the stepped portion extends from a forward edge of the ring gear and a circumferential length measured by how far the stepped portion extends around the ring gear's circumference, and wherein the first stepped portion has a different height and circumferential length compared to the height and circumferential length of the second stepped portion. 
     
     
       6. The planetary gear drive assembly of claim 5, wherein the first stepped portion has a smaller height than the height of the second stepped portion but a longer circumferential length than the circumferential length of the second stepped portion. 
     
     
       7. The planetary gear drive assembly of claim 6, wherein the second stepped portion circumferentially over-lies the first stepped portion. 
     
     
       8. The planetary gear drive assembly of claim 6, wherein the first and second stepped portions are integral continuations of the ring gear. 
     
     
       9. The planetary gear drive assembly of claim 1, wherein the self aligning means is integrally formed on the drive housing. 
     
     
       10. The planetary gear drive assembly of claim 1, wherein the self aligning means is an integral continuation of the ring gear. 
     
     
       11. A method of assembling a planetary gear drive assembly of the type having a drive housing that includes an internal ring gear located on an inner diameter of the drive housing, a planetary gear train located within the drive housing, wherein the planetary gear train includes at least one planetary gear stage comprising a central sun gear and a plurality of planetary gears spaced around and in engagement with an outer diameter of the sun gear such that rotation of the sun gear rotates the planetary gears, each planetary gear further being in engagement with the internal ring gear on the drive housing when assembled, which includes the steps of: (a) providing alignment means extending in advance of the ring gear from a forward edge thereof, wherein the alignment means forms a continuation of the ring gear only over a circumferential portion of the ring gear such that the alignment means will first contact only one of the planetary gears in the gear stage before any of the other planetary gears in the gear stage encounter the ring gear; and   (b) inserting at least one gear stage down into the housing such that the one of the planetary gears in the gear stage engages the alignment means before the other planetary gears of the gear stage engage the forward edge of the ring gear to self align all the planetary gears with the ring gear and ensure proper assembly.   
     
     
       12. A planetary gear drive assembly, which comprises: (a) a drive housing having an internal ring gear on an inner diameter of the drive housing;   (b) a planetary gear train within the drive housing, wherein the planetary gear train includes at least one planetary gear stage comprising: (i) a central sun gear; and   (ii) a plurality of planetary gears spaced around and in engagement with an outer diameter of the sun gear such that rotation of the sun gear rotates the planetary gears, each planetary gear further being in engagement with the internal ring gear on the drive housing; and     (c) a stepped extension extending in advance of a forward edge of the ring gear with the stepped extension further extending around only a portion of a circumference of the ring gear to self align each planetary gear stage with the internal ring gear as each planetary gear stage moves towards the ring gear during assembly of each planetary gear stage within the drive housing.   
     
     
       13. The planetary gear drive assembly of claim 12, wherein the planetary gear train includes a plurality of planetary gear stages with some gear stages having different numbers of planetary gears than other gear stages, and wherein the stepped extension has different stepped portions to self align all the planetary gear stages regardless of the number of planetary gears in the gear stages. 
     
     
       14. The planetary gear drive assembly of claim 13, wherein the stepped extension is an integral continuation of the ring gear.